In CSS, what happens to the text if the line-height property is set to a value lower than the current font size code example

Example: line height negative css

/* setting a line-height of 1.3em to a paragraph element with a font size of 1em*/

/* with a percentage */
p { line-height: 130% }

/* with a length */
p { line-height: 1.3em}

/* with a number */
p { line-height: 1.3}